http.Server中的端口“：http”是什么意思？

I was reading the type declaration for http.Server in the documentation and I came across this.

type Server struct {
    Addr string // TCP address to listen on, ":http" if empty
    // more...
}

If you call srv.ListenAndServe() and srv.Addr is an empty string, then ListenAndServe will pass ":http" to net.Listen (http/server.go).

What does ":http" mean?

Sometimes ports have aliases. http is 80.You can see more names here: http://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml